One of the major problems in intra-abdominal surgery is the avoidance of post-operative adhesions. It is well-known that adhesions contribute to pain, immobility, retarded wound healing, and in particular to intestinal obstruction which even may be life-threatening. In the field of gynecological surgery, post-surgical adhesions involving female reproductive organs may result in infertility.
Each surgical procedure necessarily produces various forms of trauma where the abdominal cavity or other human cavity is opened for an inspection. Physiologically, the process of wound closure then starts when bleeding ceases upon formation of a hemostatic clot at the places where blood vessels are injured. The clot, at first comprising mainly platelets, is solidified by a fibrin network resulting from the activation of an enzyme cascade involving thrombin, factor XIII and calcium. Further steps on the way to the sealing of the wound are retraction of the hemostatic clot, invasion of various cell types including fibroblasts into the wound area and eventually the lysis of the fibrin network. Adhesions are thought to begin to form when the fibrin clot covering an injury comes into contact with an adjacent surface and the new connective tissue produced by the fibroblasts attach the two surfaces together.
The problems associated with adhesions often require a further operative procedure for removing/lysing the adhesions, called adhesiolysis, which, like the first operation, principally bears the risk of forming additional adhesions.
Accordingly, the prevention of adhesion formation is medically important. Among the different approaches for prevention of adhesion formation, one involves the use of materials as a physical or bio-mechanical barrier for the separation or isolation of traumatized tissues during the healing process. Both synthetic materials and natural materials have been used as a barrier to adhesion formation. Permanent, inert implants like Gore Tex.RTM. surgical membranes consisting of expanded polytetrafluoroethylene (PTFE) generally require a second operative procedure to remove them, while others such as surgical membranes of oxidized regenerated cellulose are biodegradable, but are thought to elicit an inflammatory response ultimately leading to adhesion formation (A. F. Haney and E. Doty, Fertility and Sterility 60, 550-558, 1993).
Fibrin sealants/glues are well-known in the art for use in hemostasis, tissue sealing and wound healing, and have been commercially available outside the United States for more than a decade. Fibrin glues have not been widely used for anti-adhesion purposes. Further, the practice of changing the concentrations of thrombin and fibrinogen to achieve a fibrin film having a desired pore size is also not widely practiced.
Fibrin glues mimic the last step of the coagulation cascade and are usually commercialized as kits comprising two main components. The first component is a solution comprising fibrinogen and factor XIII, while the second component is a thrombin calcium solution. After mixing of components, the fibrinogen is proteolytically cleaved by thrombin and thus converted into fibrin monomers. Factor XIII is also cleaved by thrombin into its activated form (FXIIIa). FXIIIa cross links the fibrin monomers to form a three-dimensional network commonly called "Fibrin Gel."
Previous attempts to provide a thrombin and fibrinogen delivery device are known.
For example, one such device is disclosed in U.S. Pat. No. 4,978,336 Which discloses a dual syringe system. A device made by the assignee of the '336 Patent, Hemaedics, Inc., is sold under the tradename DUOFLO. Each syringe distal end is attached to a common manifold 14 having a mixing chamber. Fibrinogen and thrombin solutions are mixed in the manifold 14 prior to application to a wound or other surface. The manifold has a discharge tip for delivering the mixed solution onto a surface. The shortcoming of this device is the propensity for the tip to clog. This occurs when solid fibrin is formed upon brief interruptions in the application process. Such interruptions are common in normal medical procedures. The likelihood of this occurring increases as the thrombin concentration increases especially thrombin concentrations of greater than 20 IU/ml. The '336 Patent acknowledges the clogging problem and suggests solving the problem by replacing the clogged tip. (Col. 3, line 4-Col. 4, line 2). However, replacing clogged tips is impractical and unacceptable for minimally invasive surgeries where a cavity of an animal body is accessed through a small surgical opening.
Other techniques provide for applying beads of a solution of thrombin and calcium and a solution of fibrinogen and Factor XIII adjacent and in contact with one another on a surface. In this case, the thrombin and fibrinogen react primarily along interfacing surfaces while the remaining portions of the solutions are generally isolated from one another by the solid fibrin formed between them. Thus, there is inadequate mixing of the solutions to provide for a suitable fibrin film. Also, the unreacted fibrinogen is available to react with thrombin supplied by the body to promote the formation of adhesions.
U.S. Pat. No. 4,631,055 discloses another thrombin and fibrinogen delivery device having two syringes mounted in a holding frame 3 in parallel spaced relationship. A conical portion of a distal end each syringe is inserted into a connecting head. In one embodiment of the '055 patent, mixing of fluids contained in each syringe occurs inside the connecting head and in another embodiment the mixing of the fluids occurs outside the mixing head. The connecting head also includes a channel to supply medicinal gas under pressure. The medicinal gas contacts the fluids at a mouth of the connecting head and conveys the fluids contained in the syringes to a surface.
Product literature commenting on a dual syringe device for delivering fibrinogen and thrombin and sold by the Assignee of the '055 patent, reports that the device operates at gas pressures of about 30-65 psi. The momentum of the pressurized gas, especially when conveying entrained fluids, could possibly cause damage to tissue being treated by this device.
Finally, a device sold by Johnson & Johnson provided for applying a bovine thrombin and calcium chloride solution to a wound. In addition to possible issues raised by the use of bovine proteins, this procedure does not provide satisfactory hemostasis function in high blood flow situations. The thrombin is believed to be washed from the wound site by the flow of blood.
This invention overcomes these and other shortcomings in the prior art devices.